Healthy volunteers were recruited from the Old Order Amish population in Lancaster County,
Pennsylvania. After providing informed consent, research participants were screened for
eligibility. The clinical trial was designed as a randomized crossover study in which
participants underwent two frequently sampled intravenous glucose tolerance tests - one after
receiving a subcutaneous injection of saline and one after receiving a subcutaneous injection
of rapid-acting exenatide (BYETTA). The study sought to determine whether genetic variants
are associated with the magnitude of the effect of exenatide. If an association were
identified, this would help physicians to predict whether an individual patient is likely to
have a large response to the class of diabetes drugs to which exenatide belongs (GLP1
receptor agonists).